I’ve just come back from my introductory biology classroom in which I’ve been trying hard to convince students of an important historical fact: the scientists, especially the geologists, who came up with the idea that the earth was old were working in a Christian tradition, and they came up with their ideas because they needed to explain the evidence, not because they were driven by theological considerations or because they had been bribed by the Evil Atheist Conspiracy. Sometimes you just have to put them in the shoes of a geologist in 1850 to get them to see the true motives. Then I discover that ChrisR is also trying to make the point, that it’s the evidence not ideology that informs our conclusions.
It’s our studies of the rock record that have led geologists to propose that the Earth is so unimaginably old, not the edicts of the Evil Secular Conspiracy. When we observe huge angular unconformities, where rocks have been tilted almost vertically, eroded and then covered with flat-lying rocks, we see that they require a large period of time to have formed. When thermodynamics tells us that it would take tens of thousands of years for an ingneous intrusion hundreds of metres across to solidify from lava, we assume that that means it tooks tens of thousands of years to form. When present day estimates of sea floor spreading – measured in mm per year – match those estimated from the increased radiometric ages of the ocean floor away from the Mid-Atlantic Ridge, we conclude the Atlantic Ocean has been formed after tens of millions of years of slow continental drift. The list goes on and on; and useful as the fossil record is, I could continue for quite a while without having to mention the E-word.
I was also trying to get across another piece of evidence that the biologists were trying (and before Darwin, failing) to interpret, one that is quite ironic now. One of the big questions before natural historians was to explain all the gradations of form in the natural world — why are there so many species of mouse, for instance, that vary in little ways, and why are there ‘mouse-like’ forms that are larger, like rats? Why is the world swimming in transitional forms, and why aren’t animals more distinct from one another, in other words?
It’s a sign of the degeneracy of the modern creationist that instead of grappling with these questions honestly, as the 19th century creationists/natural historians did, they instead simply deny the existence of the evidence. Like Chris says, rocks aren’t coy about their age, and I’d add that organisms aren’t hiding their relationships.